What is a closed eruption surgical exposure?

Published: July 2012

Bulletin #13 - July 2012

What is a closed
eruption surgical exposure?

It is not the intention in
this bulletin to discuss the pros and cons of open versus closed exposure in
the treatment of impacted teeth in general. That will be left for another
opportunity. Nevertheless, a brief description of the two is essential for an
understanding of the differences between them. Both methods have their place
and both will produce fine outcomes when their appropriateness for the specific
case and circumstances are determined objectively, without being influenced by the
introduction of secondary considerations.

In the open eruption
technique, the impacted tooth will be open to the oral cavity at the end of the
procedure and access to it will be assured, at least in the short term. An
attachment may be placed at any time during and after the procedure and often
after some spontaneous eruptive improvement to the tooth may have occurred. This
provides the most distinct and major advantage of the method, since there if no
reason for the orthodontist to be present at the surgical episode. The
procedure is a purely surgical undertaking.

At the appropriate time,
the orthodontist refers the patient to the surgeon/periodontist, requesting
that a specific exposure be performed, depending on the location of the tooth1.
If the impacted tooth is low down in the alveolus and bucco-lingually close to
its place in the arch, then a simple “window” technique should be used, in
which a small area of overlying gingival tissue is removed, to leave the labial
surface of the tooth visible. This will leave the tooth invested with a narrow
band of attached gingiva on its labial side.

If the tooth is above the
line of the attached gingiva, then this type of exposure would leave the
impacted tooth invested labially with thin mobile oral mucosa. In this case, an
apically repositioned attached gingival flap procedure2 should be
performed to circumvent this undesirable outcome.

For a palatally impacted
tooth, where its depth under the thick palatal mucosa may be quite considerable,
occasionally reaching 10mm or more, the “window” technique usually requires
placement of a pack to prevent re-healing of the tissues over the exposed
tooth.

In direct contrast, a
closed eruption technique leaves the initially surgically exposed tooth
re-covered by soft tissue at the end of the procedure.3 Before the
surgical flap is re-sutured to its former place, an attachment must be bonded
to the tooth, in order for the orthodontist to gain access to and control over
the progress of the eruption.4

Access to the impacted
tooth is provided by the reflection of a wide flap over the immediate buccal or
palatal area concerned, the crypt of the tooth identified and a small opening
made in the dental follicle to reveal the pristine surface of the crown of the
tooth. An orthodontic attachment must be bonded to the tooth at this time and
it should be done with the minimum of further exposure of the crown of the
tooth and certainly not extended down to the periodontally-sensitive CEJ area.
The size of the exposure should be defined as the minimum area needed for the
placement of the small attachment, while providing for the blood-, saliva- and
water-free environment needed for successful bonding to the acid-etched enamel
surface.4

Although both the surgery and
the bonding can undoubtedly be performed by the attending surgeon, there are compelling
reasons for the latter procedure to be carried out by the orthodontist, despite
the fact that this makes it incumbent on the orthodontist to be present at the
exposure and to take an active part in the procedure. It runs very much against
the grain for the orthodontist to actually enter the operating theatre for the
express purpose of bonding an attachment to the unerupted tooth and, perhaps, one
may be excused for being more than just a trifle skeptical about the veracity
of the myriad of objections that most of our orthodontic colleagues offer for not
doing so. Nevertheless, as explained elsewhere,4 the advantages
overwhelmingly outweigh the disadvantages….. the more so when one takes into
consideration that it is the orthodontist who will be taken to account in the
event of treatment failure and not the oral surgeon.

Unlike the open procedure,
therefore, the closed procedure is not solely the realm of the surgeon and the
orthodontist has a prominent role to play, the benefits of which he/she will
reap in the subsequent orthodontic phase of bringing the tooth into the arch
and into alignment. Accordingly, this month’s bulletin is devoted to describing
this procedure in some detail, indicating the role of the orthodontist and
emphasizing the merit of close cooperation between the two specialists. The
only part of the diagnosis and treatment planning that will be discussed here
is directly in relation to a patient who displayed a severely displaced and palatally
impacted maxillary canine tooth, to the exclusion of other details of the
overall orthodontic condition and treatment.

Accurate positional
diagnosis

Fig. 1a, b. The panoramic and lateral skull views.

The case concerns a 14
year old girl with a class 1 occlusion and a fully erupted permanent dentition,
with the exception of the presence of a left deciduous maxillary canine. The
panoramic view (Fig. 1a) shows the left maxillary canine to be impacted high in
the maxilla, between the apices of the incisor teeth and the floor of the nose,
with its cusp tip reaching the midline raphe. The profile view, seen in the
lateral skull film (Fig. 1b), shows the canine crown to be in a continuous direct
line with the long axes of the incisors. Neither of these two films gives
adequate information regarding the spatial relationship between canine crown
and incisor root apices, nor is it possible to see if there has been any
incisor root resorption.

Fig. 2a, b. Periapical views taken at different angles
for bucco-lingual diagnosis by the parallax (tube-shift) method.

The main aim of periapical
films taken from different viewpoints (Fig. 2a, b) in the present context is to
define the bucco-lingual location of the crown of the canine, by noting differences
in superimposition of the canine crown and the incisor root between the two
films.5 Because the crown is in the same line as the long axis of
the incisors, there is virtually no discernible difference. A second aim of
using these films, often ignored, is to detect abnormality in the dental
follicle and any loss of integrity in the sharp enamel outline of the canine
crown or in the root. No abnormality was seen.

Fig. 3a-c. 3-D stills taken from the CBCT from the labial
and from the lingual aspects.

In the absence of
important information regarding the accurate 3-D location of the impacted
canine, specifically in relation to the incisor roots, a cone beam CT was
ordered.6-8 Stills taken
from the CBCT (Fig. 3a-c), both from the labial and lingual sides also
contributed information that was not available from the plane films. Finally,
the transaxial (vertical) slices (Fig. 4a, b) through the central and lateral
incisors indicated the need for a vertical and slightly posterior applied force
vector to disengage the canine from the incisors. It was clear from these views
that drawing the tooth direct to the labial archwire was an impossible task,
since the roots of the incisors obstructed this path.

Fig. 4a, b. Transaxial (vertical) slices from the CBCT
through the central and lateral incisors, respectively.

Pre-surgical
orthodontics

Typically, the first stage
of orthodontic treatment, prior to surgery, involves the leveling, aligning and
space opening of the teeth in the maxilla. This was achieved here using initial
leveling wires through to a 0.020” round stainless steel main arch and an
expanded coil spring. The coil spring was then substituted by a measured length
of stainless steel tubing of 0.036” internal diameter, which was shaped into a
gentle curve and threaded on to the archwire between the brackets of the
lateral incisor and first premolar, to act as a maintainer for the space
prepared and to add rigidity to the base arch. A 0.016” auxiliary archwire with
a vertical loop opposite the deciduous canine and a vertical offset at its
distal end, to permit passive insertion into the additional molar tube, was
prepared (Fig. 5a). A few minutes before the surgery was due to begin, this
prepared auxiliary was ligated in piggy-back fashion over the main archwire
(Fig. 5b, c).

Fig. 5a-c. The orthodontic set-up immediately prior to
surgery. Note the vertical loop in the auxiliary archwire and the distal offset
bends

Fig. 6a, b. Views at slightly different angles to show
the height of the exposed canine, in the vault of the palate in the midline
area. Note that the dental follicle of the canine was opened at the target site
and only sufficiently to accept the small eyelet attachment. The remainder of
the follicle remained undisturbed. Surgery by Prof. Nardy Caspi-Casap.

Closed eruption
surgical exposure

The surgeon opened a wide
palatal flap from the midline to the second premolar, taking care not to
involve the incisive canal, which was difficult in this case because of the
proximity of the canine to the midline suture. The reflected flap was sutured
to the canine on the opposite side and palatal bone removed until the canine
was exposed high in the palate. Figs. 6a, b should permit the reader to gain an
impression of the extreme height of the impacted tooth from the different
directions from which these two films were taken. Only a small area of the
lingual side of the canine was exposed, because of the proximity of the tooth
to the root apices of the incisors.If
an open exposure were to have been prescribed here, a much wider opening in the
palate would have been required and a pack placed. In these circumstances, it
would have been impossible to avoid damaging the incisor roots. It is also
highly doubtful if the opening would have remained patent, even with the
presence of surgical packs and the most likely outcome would have been a loss
of access to the canine – with the subsequent need for further surgery.

Bleeding from the
underside of the surgical flap and from the bared bony surface of the palate
was easily controlled, due at least in part to the adrenaline content of the
local anesthetic. Typically there was no bleeding from within the follicle and
around the minimally exposed tooth itself. The surgeon then moved to the other side of
the operating table and carefully maintained hemostasis with a fine suction
cannula, while the orthodontist dried the exposed enamel surface, applied
orthophosphoric acid gel, rinsed and dried the tooth surface with a gentle
stream of air from the triple syringe, taking care not to splash up blood on to
the tooth surface. A very small eyelet attachment already threaded with a
twisted stainless steel ligature, was then loaded with composite paste and
placed on the resin primer-prepared tooth surface, where it was LED light
bonded (Fig. 7).

Fig. 7. The eyelet attachment was bonded to the available
tooth surface.

The deciduous tooth was
extracted and the palatal surgical flap replaced after first placing a cut in
it, to permit the twisted pigtail ligature to exit in mid-palate, opposite the
location of the canine, which was hidden from sight by the re-located and re-sutured
flap (Fig. 8).

Fig. 8. The deciduous canine was extracted and the flap
replaced to cover the entire exposed area of bone of the palate. Because the direction
of traction of the canine will need to be directed vertically and slightly
posteriorly downward, the twisted steel ligature was drawn through a slit in
the flap before suturing.

With the completion of the
suturing of the flap, the surgical procedure came to an end. The last remaining
function involved activating the vertical loop of the auxiliary archwire, which
had been lying passively on the buccal side and out of the way of the surgeon.
This was swung palatally upwards, where it was ensnared in the twisted pigtail
ligature at its exit point through the replaced flap tissue in mid-palate (Fig. 9).

Fig. 9. With the flap fully replaced and sutured, the
vertical loop of the auxiliary archwire was turned inward with light finger
pressure by the orthodontist, to be held in place against the palatal tissue by
the shortened and turned over twisted steel ligature, before the patient left
the O.R.

In this way, the patient left
the operating room with light, extrusive, vertical and slightly posterior traction
force of excellent range applied to the impacted canine. It was not anticipated
that there would be any need for further active orthodontic manipulation of the
sore area for at least a month, during which time considerable positional
improvement of the canine could be expected.